In the analysis for infectious diseases or pregnancy conditions, it is common to do an immunoassay in a device having an upper compartment, a lower compartment paired with the upper one and containing a liquid-absorbing material, and a filter between them. Examples are shown in U.S. Pat. No. 3,888,629. In such devices, a trio of such paired compartments, side-by-side, allows the patient sample to be tested in one, a positive control in another, and a negative control in a third.
In such devices, a vent hole is commonly provided in each of the lower compartments, to allow air to escape as liquid is entering. By appropriately opening and closing such vent holes, an air lock can be created which will allow, or stop, respectively, liquid flow into the lower compartment from above. (Air cannot pass out through the filter either, once it is wetted.) The stoppage of flow is appropriate to allow the liquid to incubate first at the filter, before passing down into the lower compartment, as is well-known.
Prior to this invention, there has been no convenient method for manually operating the opening and closing of each of the vents. The opening and closing of each vent separately has not been conducive to easy use of such devices. Particularly this has been troublesome where the devices are sold for home use, such as in home pregnancy kits. Additionally, it is necessary, particularly in the home kits, that the vent closure be operable manually. Materials that give negligible resistance to hand movement also tend to not reliably seal off the vent. Conversely, those that provide a secure seal tend to give high resistance to a manual opening of the vent. Furthermore, if tolerances are allowed to vary, it is difficult to provide a seal that covers both the varying tolerances and stays within a desired sliding force range. Such problems are magnified if all three compartments are vented at once.